ducks with the chickens?

We just got 2 mallards today and are trying to figure out whether to build a new structure, or keep them with the chickens. We have 17 large hens and one rooster in a 6x8x10 coop with a 10x20 enclosed run. We had thought about building a separate nighttime area under the goat's deck, which would be 4'x5', and letting them run with the goats during the day and having a small fenced in pond area within the goat run. However, What about keeping them with the chickens, and adding on a 5x5' pond area that has a door that will attach it to the run? Also, could we keep the ducks in that little pond/play area from about 10am to 4 or 5pm, and then put them back into the main run for the night? If not, that how can we keep the chickens from drowning in the pool (it will either be a 1' deep kiddie pool, or a 2' deep plastic tub.)

I have 9 ducks and they live separate from my chickens for several reasons...

1 - different food requirements
2 - different space requirement
3 - most importantly, ducks add too much moisture to the coop to keep it clean and healthy for the chickens...now with only 2 you can try it but watch them because there may be hostility between the two groups and fighting.

I keep my ducks and chickens in the same run. The ducks only go in the coop occasionally to lay an egg (they use an small A-frame in the run must of the time). And I can't have water in the coop that ducks can get into or they'll play.

I feed layer pellets to everyone. I throw whole corn to the ducks and scratch to the chickens. The run is on a slope so extra water from the ducks' wading tub runs off (except for now when everything is flooding from heavy rains).

I have one indian runner duck who lives with my chickens. It works for me because

1. He was raised from a hatchling with some of my hens
2. My coop is small and raised 2' off the ground so he lives in a dog house under the coop (keeps his mess in his space)

In the summer I just throw his kiddie pool pond in the run and the chx drink out of it all summer. The only PIA part of having him in with my chx is he tries to breed the hens in the spring. He makes a bigger mess of their feathers than the rooster. But I solve this mostly but letting them free roam in the spring and summer and they seem to be able to outrun him

Our run is on a fairly steep slope also the water drains right through the run, but our chickens are extremely picky and won't even step outside the coop if there is water in their run. We were thinking about adding an addition to the end of the run that would house the ducks and a small pond during the day, so they would only be going into the coop at night. Also, in about a week they will be moving out into the housing area in a separate little enclosure. They will be housed right next to the chickens for the time being. If we introduce them to the rooster, will he protect them when they get older? All of our girls follow him around and he took on the protector right away when we got our 12 chicks